Mobile soil treatment apparatus and method

Abstract

An apparatus for treating contaminated soil is disclosed. The apparatus includes a reactor vessel for holding a volume of water which is subdivided into a first chamber and a second chamber. The chambers are in fluid communication and are partially separated by a baffle. A soil conveyor is provided for conveying a supply of the contaminated soil to the first chamber. A gas supply directs a supply of pressurized gas into the first chamber, thereby creating a turbulent mixture of soil and water in the first chamber to effect segregation of the soil into a substantially small particle size first fraction and a substantially large particle size second fraction. The reactor vessel includes a first outlet located in a lower portion of the second chamber for withdrawing a slurry comprising the second soil fraction from the reactor vessel. The lower portion of the second chamber may be funnel-shaped to help direct the mixture of soil and water toward the first outlet.

What is claimed is: 
     
       1. An apparatus for treating contaminated soil comprising a reactor vessel (10, 200) for holding a volume of water, said reactor vessel (10, 200) having at least one first chamber (12, 202) and a second chamber (14, 204); (a) a baffle (16, 206) partially separating said first (12, 202) and second (14, 204) chambers, wherein said chambers (12, 14; 202, 204) are in fluid communication; (b) a soil conveyor for conveying a supply of said contaminated soil to said first chamber (12, 202); and (c) gas supply means for directing a supply of gas into said first chamber (12, 202), characterized in that: said gas is directed into said first chamber (12,202) at a velocity sufficient to create a turbulent mixture of said soil and water in said first chamber (12, 202) thereby physically scouring the surfaces of said soil by inter-particle abrasion and liquid shear to effect separation of said soil into a substantially small particle size first fraction and a substantially large particle size second fraction; and wherein said reactor vessel (10,200) further comprises a first outlet (50, 230) located in a lower portion of said second chamber for withdrawing a slurry comprising at least said second soil fraction from said reactor vessel (10, 200).   
     
     
       2. The apparatus of claim 1, further comprising a second outlet (32, 228) located in an upper portion of said reactor vessel (10, 200) for withdrawing said first soil fraction from said reactor vessel (10, 200). 
     
     
       3. The apparatus of claim 2, wherein said second outlet (32, 228) is located above said second chamber (14, 204). 
     
     
       4. The apparatus of claim 3, wherein said gas supply means is located in a lower portion of said reactor vessel (10, 200) and directs said gas upwardly into said first chamber (12, 202). 
     
     
       5. The apparatus of claims 4, further comprising a gas outlet (233) located in an upper portion of said reactor vessel (200) for receiving gas vented from said first chamber (12, 202). 
     
     
       6. he apparatus of claim 5, further comprising a baffle (231) extending part-way across said reactor (200) between said first chamber (202) and said gas outlet (233). 
     
     
       7. The apparatus of claim 6, wherein said baffle (231) is inclined toward said second chamber (204). 
     
     
       8. The apparatus of claim 4, wherein said gas supply means comprises a nozzle (51) connectable to a supply of pressurized gas (55). 
     
     
       9. The apparatus of claim 4, wherein said soil conveyor comprises a trough (18, 208) which terminates proximate said lower portion of said first chamber (202). 
     
     
       10. The apparatus of claim 4, wherein said gas supply means comprises: (a) a windbox (203) having an inlet (220) connectable to a supply of pressurized gas (222);   (b) a distribution plate (224) comprising the upper surface of said windbox (203), said distribution plate having a pluraiity of apertures (996) formed therein; and   (c) a discharge port (227) extending vertically through said windbox into said first chamber (202).   
     
     
       11. The apparatus of claim 10, wherein said windbox (203) is generally wedge-shaped and wherein said distribution plate (224) is inclined downwardly toward said discharge port (227). 
     
     
       12. The apparatus of claim 11, wherein said apertures (226) are distributed in relatively larger numbers in the vicinity of said discharge port (227) such that the gas pressure drop along the length of said distribution plate (224) is substantially constant. 
     
     
       13. The apparatus of claim 2, wherein said second outlet (32, 228) comprises a conduit which is slidably adjustable relative to said reactor vessel (10, 200) between different vertical positions. 
     
     
       14. The apparatus of claim 2, wherein said second outlet (32) comprises a plurality of closable outlet ports (32) spaced at different distances from said first chamber (12). 
     
     
       15. The apparatus of claim 14, wherein said outlet ports (32) are located in an upper portion of said reactor vessel (10). 
     
     
       16. The apparatus of claim 15, further comprising an elongated collection tray (24) on an external surface of said reactor vessel (10) for receiving said first soil fraction passing through said outlet ports (32). 
     
     
       17. The apparatus of claim 2, wherein said apparatus further comprises a dewatering apparatus connected to said second outlet (32, 228) for removing water and any foaming reagent from said first soil fraction and recycling said water and foaming reagent to said reactor vessel (10, 200), wherein said dewatering apparatus yields a solid cake of said substantially small soil particles. 
     
     
       18. The apparatus of claim 17, further comprising a water treatment subunit connected to said dewatering apparatus for precipitating any contaminants present in said water prior to recirculating said water to said reactor vessel (10, 200). 
     
     
       19. The apparatus of claim 1, wherein upper and lower portions of said first (12, 202) and second (14, 204) chambers are in fluid communication to permit circulation of said mixture of soil and water around said baffle (16, 206). 
     
     
       20. The apparatus of claim 1, further comprising a slot (232) formed in a lower portion of said baffle (206) to permit circulation of said mixture of soil and water from said second chamber (204) to said first chamber (202). 
     
     
       21. The apparatus of claim 20, further comprising an adjustable gate (234) for adjusting the size of opening of said slot (232). 
     
     
       22. The apparatus of claim 21, wherein said gate (234) is pivotally coupled to said baffle (206). 
     
     
       23. The apparatus of claim 22, wherein said baffle (206) further comprises a skirt (241) extending from an upper edge of said slot (232) into said second chamber (204) for deflecting said pressurized gas in said first chamber (202) away from said slot (232). 
     
     
       24. The apparatus of claim 23, wherein said gate (234) further comprises an L-shaped skirt (239) at its free end which contacts said baffle (206) when said gate (234) is adjusted to a (fully closed position. 
     
     
       25. The apparatus of claim 1, wherein a lower portion of said second chamber (204) is funnel-shaped to direct said mixture of soil and water toward said first outlet (230). 
     
     
       26. The apparatus of claim 1, wherein said first chamber (12, 202) has a substantially smaller volume than said second chamber (14, 204). 
     
     
       27. The apparatus of claim 1, further comprising soil segregation means connected to said first outlet (50, 230) of said reactor vessel (10, 200) for separating said second soil fraction from water and any relatively small soil particles present in said slurry and continuously recycling said water back to said reactor vessel (10, 200). 
     
     
       28. The apparatus of claim 27, wherein said soil segregation means comprises a hydrocylone (62). 
     
     
       29. The apparatus of claim 28, wherein said soil segregation means further comprising a static column (64) connected to said hydrocyclone (62), wherein relatively large soil particles discharged from said hydrocylone (62) settle in said static column (64) against an upward flow of percolating water, and wherein said relatively small soil particles discharged from said hydrocylone (62) are withdrawn from an upper portion of said static column (64) and are recirculated to said reactor vessel (10). 
     
     
       30. The apparatus of claim 27, wherein said soil segregation means comprises at least one elongated classifier (250), wherein said relatively large soil particles settle in said classifier (250) against an upward flow of water, and wherein said relatively small soil particles are elutriated from an upper portion of said classifier (250). 
     
     
       31. The apparatus as defined in claim 30, wherein said soil segregation means comprises a series of classifiers (250) of progressively larger cross-sectional area, wherein the fluid upflow velocity in each classifier (250) is greater than any downstream classifiers (250) in the series. 
     
     
       32. The apparatus as defined in claim 1, wherein said slurry comprises said first and second soil fractions and wherein said apparatus further comprises a classifier (250) connected to said first outlet for segregating said soil fractions. 
     
     
       33. The method of claim 32, further comprising the step of recycling said first soil fraction to said reactor vessel (10). 
     
     
       34. A method for treating soil containing contaminants, said method comprising the steps of: (a) introducing said soil into a reactor vessel (10, 200) containing a volume of water;   (b) introducing a supply of pressurized gas into said reactor vessel (10, 200) to create a turbulent mixture of said soil and water; characterized in that:   said gas is introduced into said reactor vessel at a velocity sufficient to scour said soil particles by interparticle abrasion and liquid shear thereby effecting separation of said soil into a first fraction containing substantially small size contaminated soil particles and a second fraction comprising substantially large size uncontaminated soil particles, and wherein said method further comprises the steps of:     (c) withdrawing a slurry comprising at least said second fraction from a lower portion of said reactor vessel (10, 200); and   (d) separating any of said small size soil particles present in said slurry from said second fraction in a classifier in fluid connection with said reactor lower portion.   
     
     
       35. The method of 34, wherein said reactor vessel (10, 200) comprises a relatively small volume first chamber (12, 202) and a relatively large volume second chamber (14, 204) separated by a baffle (16, 206), and wherein said method further comprises the step of circulating said mixture of soil and water between said first and second chambers (12, 14; 202, 204) multiple times before withdrawing said slurry from said reactor (10, 200). 
     
     
       36. The method of claim 34, further comprising the step of dispersing a surfactant reagent into said reactor vessel (10, 200) to generate a foam comprising said first fraction. 
     
     
       37. The method of claim 34, further comprising the step of dispersing a reagent into said reactor vessel (10, 200) to alter the pH of said mixture of soil and water. 
     
     
       38. The method of claim 34, further comprising the step of dewatering said slurry and recirculating the resulting water filtrate to said reactor (10, 200). 
     
     
       39. The method of claim 34, further comprising the step of capturing gas vented from said reactor (10, 200) and recycling said gas to said reactor vessel (10, 200). 
     
     
       40. The method of claim 34, wherein said soil is introduced into said reactor vessel (10, 200) continuously and said first fraction and said slurry are withdrawn from said reactor vessel (10, 200) continuously.